Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for performing a random access procedure in a wireless communication system.
Related Art
Universal mobile telecommunications system (UMTS) is a 3rd generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). A long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.
3GPP LTE may introduce a machine type communication (MTC). The MTC is a form of data communication which involves one or more entities that do not necessarily need human interaction. A service optimized for the MTC differs from a service optimized for human to human (H2H) communications. The MTC is different to current mobile network communication services as it involves:                Different market scenarios,        Data communications,        Lower costs and effort,        A potentially very large number of communicating terminals with,        To a large extent, little traffic per terminal.        
MTC is an important revenue stream for operators and has a huge potential from the operator perspective. There are several industry forums working on an efficient M2M system with some industry members developing a new access technology dedicated for MTC. However, it is more efficient for operators to be able to serve MTC user equipments (UEs) using already deployed radio access technology. Therefore, it is important for operators to understand whether 3GPP LTE could be a competitive radio access technology for efficient support of MTC. It is envisaged that MTC UEs will be deployed in huge numbers, large enough to create an eco-system on its own. Lowering the cost of MTC UEs is an important enabler for implementation of the concept of “internet of things”. MTC UEs used for many applications will require low operational power consumption and are expected to communicate with infrequent small burst transmissions.
Meanwhile, in 3GPP LTE, a cell bandwidth can be scalable. A LTE cell supports one of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. If a UE supports 3GPP LTE, the UE should support at least 20 MHz cell bandwidth. The UE can work with any cell bandwidth. But, all LTE UEs should work in a cell of 20 MHz bandwidth. Namely, 20 MHz is the minimum UE capability that the LTE UEs should support.
Normally, an MTC device is considered as low cost device on the market. The fact that an LTE UE should support at least 20 MHz could increase cost of an MTC device supporting 3GPP LTE. Thus, it is considered that if an LTE UE operates as an MTC device, this type of LTE UE can reduce supported cell bandwidth. For instance, this type of UE may support only 1.4 MHz, 3 MHz, or 5 MHz bandwidth.
A method for performing a random access procedure and a connection establishment for a specific type of UE, e.g. an MTC device, may be proposed.